Apart from small-sized aircraft such as, e.g., light aircraft or sporting planes, commercial airplanes are customarily classified into two main types of commercial airplanes, namely, the so-called “narrow-body” airplanes and “wide-body” or large-capacity airplanes.
Narrow-body airplanes have a fuselage diameter of up to five meters and include two rows of seats separated from each other by an aisle that extends along the longitudinal axis of the airplane.
In the case of a wide-body airplane, the fuselage diameter is in excess of 5 meters. Wide-body airplanes moreover include at least two decks each containing three rows of seats, with these rows of seats being separated from each other by two aisles that extend along the longitudinal axis of the airplane.
In wide-body or large-capacity airplanes, the baggage, freight goods, etc. are usually accommodated in correspondingly provided, large-volume freight containers which are in turn stowed away in the cargo hold of the wide-body airplanes and are secured there accordingly.
In contrast, in the case of narrow-body airplanes, the baggage and additional cargo are mostly accommodated in the cargo hold in the form of loosely stacked cargo items or in smaller-sized transport chests as described, e.g., in PCT/EP03/02494 to the same applicant and published under WO 03/076267.
In order to additionally secure such loose cargo items, nettings are usually stretched in the airplanes' cargo holds in order to retain the cargo which might otherwise uncontrollably be hurled through the cargo hold in the event, say, of an emergency landing, an unexpected sudden change of direction of the airplane, violent turbulences, etc., and might thus endanger the safety of the personnel possibly present in the cargo hold, e.g. in mail planes as used by UPS etc., as well as the safety of the airplane.
The freight or cargo nettings used for this purpose are connected to fixation points on the cargo hold side by means of corresponding fixation points formed at the netting and usually having the form of belt or strap members, lugs, shackles, rings, etc., in order to divert the forces acting on the netting into the airplane's structure as tensile forces.
These fixation points on the cargo hold side are generally distributed or arranged over the perimeter of the cargo hold at spacings predetermined by the airplane manufacturer, and are attached such that the tensile forces or loads applied to them through the netting may be diverted directly into the underlying supporting structure of the airplane.
Depending on the airplane manufacturer, the fixation points may moreover be classified into different types which are in turn adapted to receive various tensile forces or loads.
Thus in the case of Airbus, for instance, the fixation points on the cargo hold side are, subdivided into so-called “net securing points” formed on the cargo hold ceiling, and “tie-down points” formed on the floor of the cargo hold. The net securing points defined by Airbus are capable of receiving shearing loads of up to 5.9 kN and tensile loads of up to 6.8 kN, and the tie-down points are capable of receiving loads of up to 8.9 kN in any direction.
In accordance with the above explanations, fixation points formed on the netting are then secured at these fixation points to thus fasten the netting in the cargo hold and introduce the force or load acting on the netting into the airplane's structure. The fixation points formed on the netting side commonly have the form of lugs, shackles, hooks, or the like, that are disposed in the marginal area of the netting.
One example for such a netting arrangement for securing baggage on the main deck of a cargo plane is known from U.S. Pat. No. 6,435,786 D1. In the case of the arrangement disclosed in this specification, a cargo net formed with radially extending meshing is inserted loose, i.e., limp, slack, in the cargo hold of an airplane in fixation points on the cargo hold side, so as to prevent an undesirable movement of the loaded cargo pieces through the cargo hold, with the netting being devised so as to optionally allow further extension when a particular limit load is exceeded.
It is, however, problematic in this type of netting arrangement that the netting can not be fastened in areas that are not provided with fixation points on the cargo hold side.
In order to nevertheless ensure sufficient securing of the cargo, it is therefore necessary to design the netting with correspondingly long portions which are then inserted in fixation points arranged further aft of the cargo hold. There may be cases, however, where it is not possible in particular areas, particularly in recessed areas such as window areas, to connect the netting-side fixation points to the fixation points on the cargo hold side even by net portions formed with a correspondingly great length.
In order to solve this problem, U.S. Pat. No. 5,915,652 A proposes a netting arrangement for securing baggage in the cargo hold of an airplane, wherein a cargo net is secured to fixation points on the cargo hold side and to additional fixation points having the form of brackets freely swinging about an axis. These brackets are pivotally linked to fixation points on the cargo hold side, provide additional fixation points to which the netting may be connected, and are intended, e.g., to bridge a window area. Similarly to U.S. Pat. No. 6,435,786 D1, the cargo net in the case of U.S. Pat. No. 5,915,652 A is also inserted into the fixation points in a loose or limp condition, i.e., without pre-tensioning.
Another netting arrangement for the cargo hold of an airplane is disclosed in EP 1 539 571 B1. Here the cargo net is attached in fixation points on the cargo hold side and additionally taken to a predetermined tension, and thus taken into a predefined shape, by means of further biasing elements that are secured in fixation points disposed further forward in the cargo hold when viewed from the netting fixation points. At the same time this is to achieve the purpose of an end portion of the net, which reaches from a fixation point on the cargo hold side to the point of intersection with the further biasing element, to have a predefined direction oriented forward in the longitudinal direction of the airplane, so that a tensile force thus introduced into the fixation point, much in the manner of a force vector, will have a predefined direction with known longitudinal and transversal or elevational components (x-, y- and z-components).
Another type of netting arrangement is moreover disclosed in WO 03/024792 A1. In this case, in order to secure cargo in the cargo hold of an airplane, a continuous, rigid frame is arranged in the cargo hold, to which the cargo net is in turn fastened.
The netting arrangement discussed in WO 03/024792 A1 implies, however, the provision of a different specific frame construction for each type of airplane, to be mounted in the respectively different cargo holds. One drawback is the relatively high cost inevitably incurred due to the numerous required frame constructions. Furthermore the additional high complexity in terms of manufacture and assembly constitutes a drawback.
However, apart from the drawbacks already enumerated in the foregoing, the netting arrangements as known from the prior art, which are predominantly employed in the so-called narrow-body airplanes described at the outset, exhibit a number of further drawbacks.
Thus it is not possible, owing to the slack, or limp, or loose attachment of the cargo nets in the cargo, to attain a homogeneous, predefined introduction of forces into all of the fixation points on the cargo hold side when a load is suddenly applied onto the netting.
In addition there is a problem as fixation points are not formed in all the locations on the cargo hold side that are necessary or desirable for this purpose in order to receive or retain netting. As a result, continuous fastening of the net can not always be achieved, so that the load having to be received and diverted by the netting will possibly only be distributed to some few fixation points on the cargo hold side; accordingly, the overall load that can be distributed is reduced, for the maximum load that may be received by one fixation point is limited.
In order to solve this problem, as related above, U.S. Pat. No. 5,915,652 A proposes the use of an adapter or shackle freely swinging about an axis in order to correspondingly furnish sufficient fixation points.
Even if additional fixation points might thus be furnished by means of the freely swinging shackle or adapter, it is not possible, due to the furthermore loose attachment of the cargo net in the cargo hold and on the shackles or adapters, to achieve a homogeneous introduction of forces into all of the fixation points on the cargo hold side.
Furthermore the solution disclosed in U.S. Pat. No. 5,915,652 A implies the drawback that due to the formation of a plurality of fixation points on these adapters, which surpasses the number of fixation points on the cargo hold side to which the adapters are secured, lastly an altogether increased load will be applied to the fixation points on the cargo hold side to which the adapters are secured in a freely swinging manner. Overloading of the fixation points on the cargo hold side is thus invited.
Finally, the netting arrangement discussed in EP 1 539 571 B1 in turn requires the presence of nets having a correspondingly dedicated design moreover having, in addition to the usual netting-side fixation points, further fixation members which may then be inserted in additional fixation points on the cargo hold side in order to pre-tension the netting in a sack-shaped configuration in the forward longitudinal direction of the airplane, as is represented, e.g., in FIGS. 1 and 2 of EP 1 539 571 B1. As an alternative, it is also possible to utilize conventional cargo nettings, however in this case it is necessary to attach additional retaining members to the netting when fitting the nets in the cargo hold, in order to correspondingly pre-tension the net; this does, however, have a negative effect on costs and makes manipulation cumbersome. Valuable cargo hold space is moreover lost due to the impressed convexity.